1. Field of the Invention
The present invention relates to telephone line test termination devices and, in particular, to a circuit arrangement which provides a unique or characteristic signature to the central office when a continuity test is made on a subscriber line.
2. Discussion of the Relevant Art
Many different types of circuit arrangements have been suggested for use in testing telephone subscriber lines from a remote location. Generally, these circuit arrangements require installation and the appearance of a telephone installer who must physically visit the premises where the telephone is installed and then signal the central office so that the central office operator may perform the required tests to determine if the subscriber lines are in working order. Many of these circuit arrangements include a switching device and a tuned circuit which is activated from the central office. These components are unreliable and require an installer to enter the home where the telephone is located. This is unsatisfactory for numerous reasons. Generally, the devices known to the applicant are unable to remain permanently at the installed telephone, or if they are capable of being installed permanently, they require activation by an AC signal provided by the central office. This approach to the problem is unreliable and therefore, unsatisfactory. A simple reliable means of providing a characteristic signature or varying impedance across the subscriber conducting paths which can provide an indication at the central office that the subscriber line is intact and operable by merely utilizing a DC test voltage and a reversing switch has not been disclosed heretofore.